1. Field of the Invention
The present invention relates to a reception AGC circuit and, more particularly, to a reception AGC circuit which converges to a target reception level in an early stage at high speed and converges, in repeating peripheral station monitoring and self-station communication, to a target reception level at each frequency.
2. Description of the Prior Art
FIG. 1 shows the arrangement of a conventional heterodyne radio receiver.
As shown in FIG. 1, a reception AGC circuit 10 in the conventional heterodyne radio receiver is comprised of a power calculating circuit 12, a feedback amplification value calculating circuit 13, and an addition amplification value setting unit 15. The power calculating circuit 12, which operates at a fixed period, cannot perform tracking operation quickly when the receiver takes a long rise time and converges to a reception dynamic range under a fading environment.
In addition, when a frequency shift occurs in peripheral station monitoring or the like or self-station communication at the initial frequency is restored, the AGC (Automatic Gain control) convergence time becomes undesirably long at the time of the start-up of the radio unit.